Method and apparatus for controlling glass surfacing tools



Sept. 28, 19 5 E. LAVERDISSE METHOD AND APPARATUS FOR CONTROLLING GLASSSURFACING TOOLS 7 Sheets-Sheet 1 Filed Aug. 16, 1952 1 .1 f w a a 2 1 3MM a 1 a 2 Z 1 555 II! I I 5 5 m fin 5 4 5 f, I 9 a E I 2 l g j b 2 I l II 2! u 2 2 8 /Hu M N 6 E s a 2 V. K M M k W D M M 7 Sheets-Sheet 2 Sept.28, 19 E. LAVERDISSE METHOD AND APPARATUS FOR CONTROLLING GLASSSURFACING TOOLS Filed Aug. 16, 1952 m e T i 1 N m 5 Z M 6. A 2T M I Z Aa 2 m M "MM/9 A M w 8 1 F. \k\ a 1 m 5 6 ,m 2 N 1. 5 j W2 0 I 0 1 8 2 74 4 1 7 2 6 2 A m 2 M A M 2 2 A 1 A nfl u I .ll w w a 4 I I J 5 I .1 O Fa i a 6; 2 a a I 5 o o 7 1 401., m5 8 4 "59/ 1 1 N 3 e 2 2 W2! 1 6 7 8Z, J I? A i AAIA m 7 a a A m Sept. 28, 1954 LAVERDlSSE 2,690,034

METHOD AND APPARATUS FOR CONTROLLING GLASS SURFACING TOOLS Filed Aug.16, 1952 7 Sheets-Sheet 3 fivEMio/L [Ivan/v [19; 54) hiss Sept. 28, 1954E. LAVERDISSE 2,690,034

METHOD AND APPARATUS FOR CONTROLLING GLASS SURFACING TOOLS Filed Aug.16, 1952 7 Sheets-Sheet 4 TV /01700- zfsma/vljauzn 315:5

4,, W W, Kid? A 4- s/vra Sept. 28, 1954 E. LAVERDISSE 2,690,034

METHOD AND APPARATUS FOR CONTROLLING GLASS SURFACING TOOLS Filed Aug.16, 1952 7 Sheets-Sheet 5 120 017,. [D/muv 1191/52/55 a a QM,

Sept. 28 1954 E. LAVERDISSE ,6 0,034-

' METHOD AND APPARATUS FOR CONTROLLING GLASS SURFACING TOOLS Filed Aug.16, 1952 7 Sheets-Sheet e Irma-dram 5M0) [Ha E: blssg Sept. 28, 1954 E.LAVERDISSE 2,690,034

METHOD AND APPARATUS FOR CONTROLLING GLASS SURFACING TOOLS Filed Aug.16, 1952 7 Sheets-Sheet 7 F .14 73a 5% Z7 92 82 Patented Sept. 28, 1954UNITED STATES METHOD AND APPARATUS FOR CONTROL- LING GLASS SURFACINGTOOLS- Edmond Laverdisse, Auvelais, Belgium Application August 16, 1952,Serial No. 304,710

Claims priority, application Belgium August 20, 1951 18 Claims. 1

In carrying into practice the simultaneous grinding and/r polishing ofthe two faces of a moving continuous sheet or ribbon of glass, it is ofmajor importance to maintain the stability of the working planes of thetools, so that they always coincide with the upper face and with thelower face of the glass sheet respectively. The glass sheet rests onmembers, generally consisting of horizontal rollers, which support andconvey it through the grinding or polishing machine. These rollersalternate with the working tools, so that the successive rollers definebetween them a series of zones, in each of which it is essential tomaintain the working surfaces of the lower tools exactly at the samelevel as the generatrices, in contact with the glass, of the adjacentrollers, because a very small diiference in level is suficient to set upin the glass sheet stresses perpendicular to its plane, which aredangerous and are likely to cause breakage thereof.

Endeavour-s have therefore been made to apply the working tools withequal pressures against the two faces of the glass, but in the knownmachines this result can only be obtained for a very short time. Infact, with the lower tools situated at the required level, the pressureis exerted on the upper face of the glass sheet by the upper toolsresting on the latter.

By reason of the principle of equality between action and reaction, thepressures on the two faces of the glass will be equal as long as thesheet situated between each pair of successive rollers lies in thehorizontal plane tangential to these rollers. Owing to the wear of thetools, which occurs mainly in grinding machines, the supporting surfacepresented to the glass by the lower tools is gradually lowered inrelation to the supporting rollers, which results in an increasingdeflection of the glass sheet.

It has therefore been necessary, for the purpose of maintaining equalitybetween the pressures, to make adjustments to the level of the lowertools at frequent intervals of time in order to restore the sheet to thehorizontal position between successive supporting rollers and thus toavoid dangerous deflection of the glass in any of the zones situatedbetween these rollers. In fact, account must be taken of the fact thatthe wear, which more or less regularly reduces the weight of all thetools, tends constantly to destroythe equilibrium between the pressures,the weight of the upper tool acting in the direction of the pressurewhich this tool must exert on the glass, while the weight of the lowertools acts in the opposite direction to the pressure which must beupwardly applied to this tool. Moreover, the deflection of the glassabsorbs some of the energy applied in the form of pressure to the uppertool, so that the unbalance between action and reaction is accentuated.

The present invention has for its object to create novel conditions forthe control of the movements of the tools towards the glass which permitof correcting the unbalance resulting from wear, and not only ofpermanently maintaining the constancy of the level of the working planesof the grinding tools (irons) and/or polishing tools (polishers), butalso of constantly restoring the initial pressure exerted by the toolson the glass. It it based upon the novel idea of acting both on theupper tools and on the lower tools to adjust their respective positionsconstant- 1y without resorting to periodical adjustments, and ofpermitting them, under the action of the forces applied thereto, tomaintain themselves in the respective working planes determined by therollers or other supporting members in the case of the lower tools andby the thickness of the glass sheet in the case of the upper tools. Theinvention also concerns the provision of automatic apparatus forobtaining this result under conditions of absolute safety.

To this end, in the method according to the invention, there aredirectly and continuously applied to the lower tools, which are arrangedto be capable of freely moving towards the glass sheet, pressures whichare opposite and equal to the pressures exerted by the upper tools and,in order to maintain equality between these pressures, the unbalance dueto the wear on the tools is constantly compensated for by modifying thedownward and upward pressures in opposite directions in order to bringthe opposite tools into their respective working planes at each instant.This method may be applied individually to each pair of opposite tools,or to each group of tools, for example to the two groups of toolsmounted respectively on the upper beam and on the lower beam of onepair. In the latter case, if one tool has become more rapidly worn thanthe other tools of the same group for any reason, for example owing toirregularities in the feeding of the abrasive composition, this toolwill work less actively until the instant when the wear on the othertools of the same group has reached the same point.

Since the tools or groups of tools are constantly pressed against theglass and to some extent constitute floating supports for the glass,precautions must be taken to ensure that an accidental drop in thepressure on one tool or group of tools does not result in the sheet ofglass being depressed by the opposite tool or group of tools. It is alsonecessary to ensure that disturbances in the'feeding of abrasivecomposition or the accidental presence of unevenness on the surface ofthe glass, do not produce any resistance to the forward movement of theglass sheet which might be sufficient to cause breakage thereof.

In the apparatus according to the invention, the lower tools aresupported by members which are constantly urged to move towards theglass.

In addition, members controlled by the movements of the tools towardsthe ribbon of glass act in the required direction for correcting, i. e.modifying according to requirement, the pressure of the upper and lowertools with a view to equalising them. These corrections may be exertedin a simple and convenient manner by mechanical means, but it is alsopossible to use other means, such as hydraulic means, to advantage.

According to the case, safety abutments and/or locking devices areprovided to prevent untimely reversal of the movement of the toolstowards the glass in the event of deficient pressure.

When an abnormal resistance is set up to the forward movement of theglass sheet, an immediate relaxing of the pressure is brought about.According to one feature of the invention, there is utilised for thispurpose the dependence lee-- tween the resistance to the rotation orother appropriate movement of the tools and the pres sure of the toolson the glass, and the latter is relaxed under the control of theincrease in the resistance to the actual movement of the tools on theglass. This relaxation is preferably progressively produced up to agiven point, whereafter a reversal-of the direction of the pressure isproduced if the resistance continues to increase.

The invention is particularly applicable to grinding or polishingmachines, in which the tools consist of discs mounted on rotative shaftsmounted in beams or supported disposed in pairs, one above and one belowthe sheet or ribbon of glass.

An embodiment of the invention particularly suitable for thisapplication consists in control" ling the rotation of the tool or toolsmounted on a support or beam by means of an electric motor, the feedcircuit of which controls apparatus which, under the influence of theincrease in the resistance to the rotation of the tools, produce therelaxation of the pressure applied to the tool or tools. When the latterare forced against the glass by a hydraulic pressure, the latter ispreferably first gradually reduced in order that it may be readilyrestored if the disturbance of the normal operation of the apparatus isonly slight and temporary. If this partial relaxation is foundinsuflicient, the control means so act as to reverse the direction ofthe pressure, that is to say, to move the tools away from the surface ofthe glass.

In the installations for the simultaneous grinding and/or polishing ofthe two faces of the glass, the compensation and safety means accordingto the invention may be applied either to the upper tools or to thelower tools, or again to both.

In the accompanying drawings,

Figure 1 is a diagrammatic elevational View showing the deflection ofthe glass sheet due to the wear on the tools in the known machines.

Figures 2 to 15 show by way of example apparatus according to theinvention, Figure 2 showing in vertical section an arrangement forcompensating for the wear applied to two irons Working on the oppositefaces of a glass sheet,

Figure 3 is a vertical section showing a modification,

Figure 4 shows diagrammatically a hydraulically controlled compensatingarrangement,

Figure 5 is a longitudinal vertical section through a pair of beamsequipped with a series of irons and wear-compensating mechanisms,

Figure 6 is a longitudinal vertical section through a lower beamaccording to another arrangement,

Figures 7 and 8 are a vertical section on the line VIIVII of Figure 6and a partial horizontal section on the line VIII-VIII of Figure 7,

Figure 9 is a diagrammatic view of two toolsupporting beams in verticalsection taken perpendicularly to the direction of forward movement of asheet of glass subjected to grinding on both faces,

Figure 10 is a plan View of the lower beam illustrated in Figure 9,

Figure 11 is a diagram of the electric circuits and of the hydrauliccontrol of the irons,

Figures 12 and 13 are respectively axial sections through the regulator,and through the reversing device and the distributor which are employedin the hydraulic control of the irons,

Figure 14 is a longitudinal section through the pressure blockingdevice, and

Figure 15 is a transverse section on the line XVXV of Figure 14.

In Figure 1, there are shown at i and respectively, upper and lowersupports or girders, in which there are mounted in known manner rotativeshafts 2, 2 supporting the upper and lower working tools (irons orpolishers) 3 and 3 respectively which act on the glass sheet a supportedby horizontal rollers Q, of which those which are close to the pairs oftools 3, 3' cooperate with upper rollers 9 for the continuous drive ofthe sheet a in the direction of the arrow b.

Owing to the wear on the lower tools, the level of their workingsurfaces is gradually lowered, whereby a deflection of the glass sheetindicated (in exaggerated form) at c is produced in each zone a situatedbetween the rollers t on either side of each pair of tools, under theaction of the upper tools, the weight of which presses con-- stantly onthe glass.

When the difference in level reaches certain limit, for example 2 to 3it is necessary to return the lower tools to their initial level inorder to avoid the danger of breakage. In practice, it is preferred toraise these tools slightly beyonstl the ideal working plane, thuscreating in the glass a deflection in the opposite direction to c, inorder to reduce the frequency of adjustment. Such adjustment must nevetheless be e 'cxi mately every two hours in grinding which an amplitudeof wear of '7 cm., for ple, can be permitted or an iron of a thhlrnessof 18 cm., before scrapping the tool.

lhe necessity for making these frequent adjustments is avoided when useis of means according to the invention, a first ple of which is shown inFigure 2. In this gure also, I designates a beam or other support inwhich there is mounted the vertical shaf hic supports the upper iron theiron 5 is set in rotation by a l with a toothed wheel 5 actuated by apinion by means of the auxiliary shaft and .i. The tool-supporting shaft2". can slide in the sleeve 4, which drives it in its rotation throughthe key it.

The pressure exerted on the glass by the iron 3 is here represented bythe weight of the latter and of its shaft 2, as also of a sleeve iiresti. through a ball thrust hearing it, on a shoulder E3 of the shaft2. The said sleeve, which the shaft 2 turns freely, is provide with tworacks i4 each engaging with a pinion 55 mounted on a bracket it securedto the wall of the support 1. Keyed on the pin ll of each pinion i5 isan arm 48 carrying a weight 19.

I5 and their pins H in the direction of the arrows 20. As the pressureexerted by the weights [9 on the sleeve His proportional to the cosineof the angle of inclination of the arm l8 with respect to thehorizontal, it will increase in proportion as this angle decreases, thatis to say, as the weights [9 are lowered, if their displacement ismaintained in the substantially rectilinear centre portion of the cosinecurve. It will therefore be sufficient to dimension the weights ill, thearms [8 and their angle of inclination with a new iron in such mannerthat the reduction in the weight of the said iron is automaticallycompensated during its operation for by the increase of the pressureexerted by the weights It.

In order to raise the shaft 2 with the iron and to lower it in order tobring the iron into contact with the glass, an externally screwthreadedsleeve 2! is provided, in which the shaft 2 can freely slide. The threadon this sleeve meshes with the internal thread on a worm wheel 22 whichin turn meshes with a worm 23. The rotation of the worm 23 in onedirection or the other therefore has the effect of raising or loweringthe sleeve 2! along the shaft 2. The latter is provided at its upper endwith an abutment 24 having a ball bearing mounted thereon. If, in theposition shown in the drawing, it is desired to raise the iron 3, theworm 23 will be actuated in I weights 2%.

The arrangement of the members for the control of the lower iron 3' issuch that this iron is individually pressed against the glass. Thisarrangement is here similar, in its broad out" line, to thathereinbefore described with reference to the upper iron and thecorresponding members bearing the same reference numerals provided withthe index but the following differences are to be noted:

(a) Since the lower iron must press on the glass in the upward directionin order to balance the pressure of the upper iron 3, a counter-weight25 is here used to exert this counter-pressure. This counter-weight 25is suspended from cables 25 which pass over pulleys 21 and are attachedto a ring 28 which i provided with a ball thrust bearing 29 on which ashoulder 30 of the shaft 2 rests.

(b) The weights 19' are so disposed as to act in a direction opposite tothe constant thrust exerted by the weight 25, that is to say, in suchmanner as to compensate for the reduction in the weight of the iron 3'due to wear., The sleeve II is downwardly extended as far as the ring 28on which it bears.

In the constructional form shown in Figure 3, in which the samereference numerals designate the same parts as in Figure 2, thearrangement for raising the upper iron is replaced by a hydrauliccylinder 3!, the piston 32 of which drives the shaft 2 through the ring33 when the oil under pressure is admitted below the piston through theduct 34 in order to lift the iron 3,

6 the lowering of the iron taking place under the action of its ownweight.

The arrangement for pushing the lower iron 3 comprises, instead of thecounter-weight 25, a hydraulic cylinder 3|, the piston 32' of which actson the shaft 2' through the ring 33. In order to avoid a violent thruston the glass in the event of the upper iron not being in position, anabutment may be provided to limit the upward displacement of the iron3'. In the example illustrated in Figure 3, this abutment, which isdesignated by 35, is situated at the base of the hollow rod 36 of thepiston 32. A pre-adjusting device controlled by screws 2|, 22, 23 isdisposed at the lower end of the shaft 2' and the abutment 35 stopsagainst the base of the sleeve 2 I if necessary.

In order that the iron 3 may not fall back in the event of deficientpressure in the duct 34 for feeding the cylinder 3 l this duct may beprovided with a device 92 comprising a non-return valve or ball. Thedanger of depression of the glass sheet under the thrust of the iron 3is thus avoided.

The reduction in the pressure exerted on the iron in order to allow forthe wear may also be obtained by acting on the hydraulic pressure in thecylinder 3 I In the example of Figure 4, this pressure reduction isobtained by the gradual opening of a needle valve 31 disposed in adischarge pipe 38 connected to the duct 34 for feeding the cylinder 3!.The needle 3'! is here controlled by the rack [4, the toothed sector l5and the lever 39 linked on the one hand at 40 to the fixed bracket i6,and on the other hand to the stem of the needle 3'1 by an adjustablearticulation 45.

Figure 5 shows a pair of beams I, I in which a number of tools 3, 3' aremounted side-by-side, and are constantly pressed against the glasssheet, the upper tools by their own weight, for example, the lower toolsby a hydraulic pressure exerted in the cylinders 31 similar to those ofFigure 3. Each shaft 2 is provided with an individual verticaladjustment device 2|, 22, 23' controlled by a hand wheel 54'.

Compensating means comprising oscillating weights l9, l9 and racks I I,ll correct the pressure of the tools 3, 3' on the glass as a function ofthe weight reduction due to the wear. The rotation of the shafts 2, 2'is controlled by motors 5! 50', through the horizontal shafts 55, 55 andthe gears 8, 8 and 5, 5.

When applied to a polishing machine, an arrangement such as that shownin Figure 5, in which the vertical displacement of each lower tool isindividually controlled, is particularly advantageous because it enablesthe lower tools constantly pressed against the lower face of the sheetto reach the glass at the base of the depressions which, when theyoccur, frequently escape the polishing in the existing machines.

It is also possible, in accordance with another embodiment of theinvention, to make the tools mounted on a common support or beamintegral in their vertical displacements. In Figures 6 to 8, the shafts2' of the iron 3 of the lower beam l are mounted on a cross member llthrough screwthreaded sleeves 42' actuated by manual control meanscomprising worms 48' which permit their individual vertical adjustmentin the cross member H by the initial position of which can in turn bevertically adjusted by the screw device 43', which is actuated by handor by a servomotor. The cross member 4|, which is guided 7 betweenvertical slide ways it, is forced upwardly against the glass sheet a bythe hydraulic piston 53'. Wear-compensating devices 44' comprisingoscillating weights ie' similar to those shown in Figures 2 and 3 bearon the beam is through brackets l6 and act on the cross member llthrough racks Hi.

If at any instant one of the tools 3 is worn to a greater extent thanthe other tools of the same beam, the work of this tool will be sloweddown or stopped until the other tools have reached. the same degree ofwear. The same arrangement may obviously be employed in the upper beam.

Figure 9 shows at i and respectively an upper beam and a lower beamwhich are supported in known manner by frames (not shown) on either sideof the glass sheet a resting on the horizontal rollers Q (Figure 10),the generatrices of which determine the horizontal working plane of thelower tools 3.

Mounted in the upper beam l are vertical rotative shafts 2, one of whichsupports an iron 3 and the other a disc ill on which is mounted a groupor set of three irons 3, this arrangement obviously being capable ofvariations as required.

The shafts 2 are provided with vertical adjust ment devices it andsupported by a cross member ll vertically guided in the slideways '56.The tools ll having previously been brought to the same level by thedevices 48, the required pressure is exerted on the glass at by theadmission of oil under pressure into the cylinder ii above the piston 53through the duct 5! until it comes into contact with the glass sheetresting on the rollers a! the oil below the piston 53, while the ductsbio and 52 serve respectively for the application of the pressure underthe piston 53 and the discharge of the oil above the piston The shafts 2are set in rotation by an electric motor 5% through auxiliary shafts 55and l (Figure 9) and gears 5.

The arrangement of the lower beam 2 and of the members which it supportsis similar to that hereinbefore described, and the same numerals, withthe index have been employed for the said parts as for the correspondingparts of the upper beam. For the rotation of the shafts 2, the auxiliaryshaft 55 (Figures 9 and 10) is actuated with the aid of the pinions 5tby a stub shaft 58 connected by a coupling be to a stub shaft 58directly actuated by the motor 58 with the aid of the pinions 56. Whenthe tools 3 have been set to the required level by the devices iii andthe cross member ll has been adjusted to its initial position by thedevice 33, the oil under pressure is admitted into the cylinder is,below the piston 53, preferably at the same time as the admission intothe cylinder it. A single pair of ducts 5!, 52 is here sufficient forthe application of the pressure below the piston 53 and the discharge ofthe oil above the piston 53, because as soon as the pressure is relaxedat El, the piston 53, the cross member 4 l and the irons 3 descend againunder the action of their own weight.

It is always essential for the irons 3, 3, which are preferably (but notnecessarily) situated exactly opposite one another, to be appliedagainst the glass with equal and constant pressures. For this purpose,the cylinder its, for moving the lower tools has a larger diameter thanthe cylinder 49 of the upper beam, since the pressure in the cylinder 49must overcome the weight of the cross member GI and of the lower tools,while The duct 52a is provided for the discharge of I the weight of thecross member ill and of the upper tools is added to the pressure in thecylinder 49. In order to prevent the wear of the tools in the course oftheir operation from destroying the equilibrium of the pressures on theglass, the cross members ll, l i are provided with compensating devicesti l, lit similar to those shown in Figures 7 and 8.

In order that an accidental relaxation of the pressure in one of the oilsupply ducts 5 l 5 l may not result in an unbalance capable of causingbreakage of the glass sheet, non-return devices e2, 92 for example ofthe ball type, are disposed in these ducts. Such a device is shown inFigures l l and 15, in which a chamber till containing the ball S4 isprovided with two seats separated by a distance adjustable with the aidof the sleeve 98. One of the seats, the seat is closed by the ball whena counter-pressure is set up, while the ball is normally applied againstthe other seat 96 which permits the passage of oil in the direction ofthe arrow. If the feed pressure only decreases slightly, the ball movingslowly towards the seat t5 will permit the discharge of a quantity ofliquid depending upon the distance between the seats. In the event of asudden pressure drop in the duct 5! or or of an increase in pressure inthe cylinders '59, 59, the ball will be returned on to its seat morerapidly but with a suficient delay to permit retraction of the irons,for example by an amount of 0.1 to 0.5 mm. as well as the tripping of asafety device such as that hereinbefore described.

The oil intended to feed the cylinders 39, 5 is drawn from a tank til bya pump iii which delivers it into an accumulator 62, whence it passesthrough the duct 63 into the pressure regulator 84 (Figures 11 and 12).During normal operation, the oil under pressure enters through 653 andleaves through 85 after having passed through the chamber 66, in which athrottle piston er, the position of which is vertically adjustable bymeans of the rod t8, determines the date of flow of the oil from theoutlet duct and surplus being admitted through the springloaded valve 68into the discharge duct Sta and returning to the tank till.

From the duct 85, the oil at the required pressure is normally admittedthrough the duct it into the chamber H of the reversing devices l2(Figures 11 and 13) in order to be sent through the duct 51 into theupper chamber is above the piston 53, while the oil situated below thepiston 53 returns to the tank Bil through the ducts 52a and 53a.

Connected to the pressure duct 65 is a duct i l which passes the oilunder pressure through the distributor l5 and the duct 5! into the lowercylinder i9 below the piston 53, in the position illustrated in thedrawing, which corresponds to normal operation. The return duct 52 isthen cut off from the discharge duct l3 leading to the tank 6!].

The upper part of the rod 68 of the regulating piston 657 isscrewthreaded and engaged in an internally threaded wheel it which ismounted in fixed bearings ll and meshes with a toothed wheel l8controlled by a motor 89 (Figure 11).

The reversing device l2 and the distributor iii are provided withpistons l3, M respectively, supported by a common rod 32, thescrewthreaded end of which is engaged in an internally threaded wheel 83which is mounted in fixed bearings 8d and engages with a toothed wheel35 controlled by a motor 90.

The starting of the motor 80 will thus have the effect of operating theregulator 64 and the starting of the motor 90 will have the effect ofoperating the reversing device 12 and the distributor I5.

During normal operation, the iron-supporting cross members 4!, 4| moveprogressively in the direction of the constant pressures which areapplied thereto, these movements being limited to the compensation forthe wear of the irons, the said pressure being balanced and maintainingthe constancy of the working planes of the tools on the glass. Undernormal conditions of pressure, speed and feed of abrasive composition,the power absorbed by the motor 50 controlling the rotation of the toolsis normal. However, if a disturbance occurs, for example in the feed ofabrasive composition to the tool, or abnormal resistance due to localeizcessive thickness of the glass, jamming of the tools is likely tooccur, which will bring about breakage of the glass by opposing theforward movement thereof.

These modifications of the working conditions are immediately manifestedby an increase in the resistance opposed to the motor 50. The circuitsillustrated in Figure 11 show how-the increase in the absorption ofpower by the motor 50 may be utilised to bring about the successivestarting of the motors 80 and 90.

In the feed circuit 86 of the motor 50 connected to the supply there isconnected the primary winding of a transformer 88 such that if thismotor absorbs 50 ampere in normal operation, the current induced in thesecondary circuit 81 is, for example, 0.5 ampere. Connected in thiscircuit 81 are the coils B, BI, B2, B3, B4 and B5 of electro-magnets,the respective spring-loaded armatures C, CI, C2, C3, C4 and C5 of whichare separated from the cores by air gaps of increasing lengths adjustedby the screws 89, in order that these armatures may be successivelyactuated immediately the induced current flowing through the circuit 81increases to a sufficient extent.

The coil B controls through its armature C the closing of the feedcircuit 9| of the motor 80. As long as the current in the circuit 81remains in the neighborhood of the normal value of 0.5 ampere, noarmature will be attracted. If the load on the motor 50 increases andthe current in 87 reaches 0.55 ampere, the coil B closes, through itsarmature C, the circuit 9| which feeds the motor 30 through the seriesresistances RI, R2, R3 and R4. The motor 80 is slowly started andproduces a slow movement of the regulating piston 61 in the direction ofa reduction of the pressure applied to the pistons 53, 53.

If, despite this action, the power absorbed by the motor 50 continues toincrease, the current in the circuit 81 will become sufficiently strongto close the armature CI, which will short-circuit the resistance R! andwill then act on the armatures C2, C3, C4 in order to short-circuit theresistances R2, R3 and R4 successively and to accelerate the movement ofthe motor 80.

If the pressure reduction thus produced is still insufficient to stopthe increase of the current in the circuit Bl, a coil B5 is energisedand closes, through its armature C5, the feed circuit 91 of the motor526. The latter raises the rod 82 and its pistons I9, 5! which close theducts 5i, 52a and 5I, and open the ducts 5m, 52 and 52', thus producingthe reversal of the pressure in the cylinders 49, 49' and moving thetools 3, 3' away from the glass. 7

As long as the motor 90 has not been started, it is desirable for therestoration of the normal pressure to take place automatically, in orderthat any brief disturbance may not interrupt the normal operation of themachine. To this end, there is connected to the supply 51 (Figures 11and 12) a circuit 99 which comprises the winding of a coil B6, thecontacts 508 and the conductor segments IOI, I02. Normally, this circuit99 is closed at I00 by the armature C, but it is open at IOI, I02.

Mounted at the upper end of the rod 68 of the regulator 64 is a rack I03which meshes with a pinion 504 on which a brush I05 is keyed. When, as aresult of abnormal resistance to the operation of the motor 50, the coilB closes the circuit 9|, its armatures simultaneously break the circuit99 at I00 and the rod 68' of the regulator moves upwardly, the motor 8i}turning in the direction of a pressure reduction in the cylinders 49,40'. The brush E05 is thus moved over the segments IOI, I02 extendingover a predetermined part of its travel, past a scale I06 indicating thevalue of the pressure.

If the resistance to the rotation of the motor 50 returns to normalwhile the brush it is connecting the contacts IOI, I02, the contacts ofthe armatures C4, C3, C2, CI and C are closed again and the circuit 99is closed by the contacts I00. The coil B6 then closes the contact C6connected in a circuit I01, which reverses the connections of the motorto its feed circuit 9i and produces the rotation thereof in thedirection of the increase of the pressure in the cylinders 49, 49. Thisoperation continues until the circuit 99 is broken by the separation ofthe brush I05 from the contact segments IDI, I02, normal operatingconditions then being restored.

If, on the other hand, the disturbance which has brought the motor 80into operation persists, the motor is started in order to reverse thepressures on the pistons 53, 53 and the manual intervention of theoperating personnel becomes necessary in order to restore normaloperation after the current has been cut off. For this purpose, switchesI08, I09 and H0 are provided to enable the operators to break thecircuits 06, 8'! and 99 respectively, switches l I I, II2 to break thecircuits 9| and 91 respectively, and switches H3, I I4 to connect themotors 80 and 90 respectively, temporarily to the supply 51 in order toreturn the regulator 64, the reversing device 12 and the distributor I5into their initial positions in order to enable the work to be resumedunder the control of the automatic safety arrangement.

Naturally, the form of the beams or supports I and the details of thevarious mechanisms and devices described with reference to the drawingsmay be modified without departing from the scope of the invention.

I claim:

1. Method of controlling vertically movable upper and lower workingtools simultaneously surfacing both faces of a horizontally moving glasssheet in a glass surfacing machine; said method comprising the steps ofapplying a downward pressure to the tools operating on the top face ofsaid sheet and an upward pressure to the tools operating on the bottomface of said sheet and balancing said downward pressure by adding tosaid downward pressure of the upper tools an increasing pressurecompensating for the loss of weight due to wear of the upper tools,

11 and subtracting from said upward pressure exerted on the lower toolsan increasing pressure compensating for the loss of weight due to wearof the lower tools.

2. In a method as claimed in claim 1, locking the tools against backwardmovement away from the surface of the glass beyond a predeterminedtolerance.

3. In a method as claimed in claim 1, rotat ing the working tools abouttheir respective axes and relaxing said downward and upward pressuresapplied to the upper and lower tools, respectively, in case of abnormalresistance 30 the rotation of the tools.

l. In a method as claimed in claim 1, rotating the worlring tools abouttheir respective axes, relaxing said downward and upward pressuresapplied to the upper and lower tools, respectively, in case of abnormalresistance to the rotation of said tools, and reversing said pressurescontinuation of the abnormal resistance beyond a predetermined value.

5. In a method as claimed in claim 1, rotating the working tools abouttheir respective axes, relaxing said downward and upward pressuresapplied to the upper and lower tools, respective ly, in case of abnormalresistance to the rotation. of said tools, and restoring said pressuresif the abnormal. resistance vanishes before it reaches a predeterminedvalue.

In a s .rfacing achine, the combinaof means for feeding a hosontal.sheet of vertically movable surfacing tools for operating on both facesof said sheet, means for applying a downward pressure to the toolsopera-ling on the upper face of said sheet and means for ap plying anupward pressure to tools operating on the lower face of said sheet andbalancing said downward pressure, means for addirn and subtracting fromsaid downward and upward. pressures, respectively, dependence on thewear of tools to compensate for any unbalance such wear.

7. In a glass surfacing machine, the combination of means for feeding ahorizontal sheet of glass, vertically movable surfacing tools foropcrating simultaneously on both faces of said sheet, said toolscomprising upper tools and lower tools, means for applying a downwardpressure to said upper tools, means for applying to lower tools anupward pressure balancing said downward pressure, means for adding tosaid downward pressure an increasing pressure to compensate for the lossof weight clue to wear of the upper tools, and means for subtractingfrom said upward pressure an increasing pres sure to compensate for theloss of weight due to wear of the lower tools.

8. A glass surfacing machine as claimed in claim 7, said wearcompensating means each ising pivoted weights, pinions andrackscontrolled :by the vertical movements of said tools.

9. A glass surfacing machine as claimed in claim 7, wherein hydraulicmeans are provided for applying pressure to said tools and said wearcompensating means comprise a discharge Valve responsive to themovements of the said tools to control said hydraulic pressure means.

10. A glass surfacing machine as claimed in claim 7, wherein anadjustable abutment is provided to limit the movement of each tooltowards the glass.

11. In a glass surfacing machine, the combination of means for feeding ahorizontal sheet of glass, pairs of vertically movable supportsextending horizontally across the path of said glass sheet, each paircomprising an upper support and a lower support, surfacing tools on bothsupports of each pair, means for applying a downward pressure to saidupper support and means for applying an upward pressure to said lowersupport, means for adding to said downward pressure an increasingpressure to compensate for the loss of Weight due to wear of the toolson said upper support, and means for subtracting from said upwardpressure an increasing pressure to compensate for the loss of weight dueto wear of the tools on said lower support.

12. A glass surfacing machine as claimed in claim 7, wherein hydraulicmeans are provided for applying pressure to said tools, said hydraulicmeans comprising a non-return valve so arranged as to act with a slightdelay to permit a slight retraction of the tools.

13. A glass surfacing machine as claimed in claim 7, wherein thesurfacing tools are of the rotating disc type, comprising vertical forsaid tools, means for rotating said chats, and supports carrying saidshafts and said pressure applying means.

14. A glass surfacing machine as claimed claim 9, comprising safetymeans responsive to the pressure exerted on the glass by a tool forreleasing said pressure when it exceeds a predetermined value.

15. A glass surfacing machine as claimed in claim 11, wherein thesurfacing tools are of the rotating disc type, comprising verticalshafts for said tools, means for rotating said shafts, said shafts beingcarried by said supports, and electrically controlled safety meansresponsive to the pressure exerted on the glass by a tool for releasingsaid pressure when it exceeds a predetermined value.

16. A glass surfacing machine as claimed in claim 7, wherein thesurfacing tools are of ti. rotating disc type, comprising electric motefor rotating said tools, one such motor rotau. a pair of oppositely,disposed tools, and safety devices controlled by said electric motors fr simultaneously relaxing excessive local sure exerted on the glass byany pair of oppositely disposed tools when the resistance to rotation ofsaid tools exceeds a predetermined value.

17. A glass surfacing machine as claimed reversible means fortemporarily reduci local pressure exerted by any pair of tools on glass.

18. A glass surfacing machine as claimed in claim 16, wherein eachsafety circuit comprises means for temporarily reducing the localpressure exerted by the pair of tools on the glass means for reversingsaid pressure if it increases beyond a second predetermined value.

References Cited in the file of this patent UNITED STATES PATENTS

